Alternating-current meter.



PATENTED OCT. 11, 1904.

W. H. PRATT.

ALTERNATING CURRENT METER.

APPLICATION FILED MAE3,1903.

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inventor.

Wilam H. Pratt.

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UNITED STATES Patented October 11, 1904.

PATENT OEEICE.

W'ILLIAM H. PRAT", OF LYNN, MASSACHUSETTS, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK,

ALTERNATlNG-CURRENT METER.

SPECIFICATION forming part of Letters Patent No. 771,932, dated October 11, 1904. Application lad March 3,1903. Serial No. 1145.932. (No model.)

,To (all, wwn t may concern:

Be it known that 1, VLLLIAM H. PRATT, e citizen of the United States, residing nt Lynn, county of Essex, Stute of Messnchusetts, have invented certain new and useful Improve ments in Alternnting- Current Meters, of which the following is n spccilicntion.

My invention relates to certain improvements in electric meters, and more particu- IO lairly in siternutingcurrent meters of the in duction type.

The features of novelty which characterize my invention l have pointed out with particu.- lnrity in the appended claims, while the invention itself es exemplilied by one of the numerf ous embodiments of which it is capable I have set forth as to detail and mode of operation in the following specification, which is to be teken in connection with the accompanying 2o drawings, in which- Fignre 1 issview, partly in cross-section. of a meter embodying my invention; Fig. 2,3. View of a part of the meter shown in end elevation in Fig. 1, and Fig. 3 n plan view of a.

detail shown in side elevation in Fig.. l.

In Fig. 1 the frame or casing for supporting the working parts of the meter is indicated at 1. The cover for inclosing the work'- ing pnrts of the meter is indicated at 2 and is held in position by any suitable means-as, for exanipie, by clamping-bolts, such es 3. The binding-posts or other securing devices for the conductors lending into the meter are secured to the frame or casing 1, es indicated et 4, and access may be had to these conductors without removing the cover 2. This eccess is aiforded by en opening in the cover 2, which opening is closed by a plate 5, held in position by the clamping-screw 6, one end of which passes through e rib 7, extending across the openingfor which the ,plete 5 serves esima-,overl The wells of. this opening arein- Iizlicxe'nn'aiil 'so ei: lass-,mete bmbivi dotted Linesmti. y

The motive element acts upon the rotating disk 9, constituting the movable member ot' the meter, by means of e combination of inegnetic fluxes dce to the load-current and the potential-current of the meter. The flux due to the potential-current is produced by means 5 5 of a potential-coil 10, connected in shunt with the mains 11 12 of the system in which energy is to be measured by the meter. This potential-coil 10 is mounted. upon e core of megnetic material 11', having a magnetic circuit, 60 which would be completely closed except for a smellslot or nir-gap 12. The limbs of the magnetic core are preserved in lixed relation to each other by means of a. pin 13 of some non-magnetic material-such, for example, us German silver--driven between Athe walls ot' the slot, as indicated. The slot is thus pre vented from closing up or` otherwise altering its dimensions under the inuence of magnetic or any other stress towliich the core 7G may be submitted in practice. The core is provided with two polar projections 1415, located, respectively, on either side of the airgap 12, as indicated. These polar projections are provided with phase-adjusting windings in which secondary currents are induced by the action of the megnetomotive force of the potentiel-winding 10. The windings may be connected in series with each other in a closed circuit. An adjustable resistance or resist- S0 anceswsnch, for example, et lfis employed to adjust the currents liowing in the plmscadjusting windings.

`The meter is provided in the present instance with a. single-current coil. (Indicated S5 at 19.) T his current-coil has an inverted-T- shaped magnetic core, the vertical limb Dt' Wbiclris indicated in dottedfilines at 20 and theb'crizontel member at i214' The currentcoih is -plsced about the verticdl limb of the .cordes indicated.' Thisnvertcel pertf the icererisipncnideidnnvithz twoffpelripmiectiehs s2-@niliiarrneedlcpnositeitheipolnr'iorcw ricerca Mend iottbeshreef the potentielfcoili f licseipeilatsproectlcneioinrthienreief ihecm'ret-ceibremrrdeddcftheicthwlinx may be uniform in distribution between'fithe icprescf the petentialiendmiwrentceilmsathat o the constantof the meter will not be changed by a shifting of the disk toward one core or the other` The two cores above described are supported on a skeleton framework 24, which is sandwiched in with the laminations of the respective cores, as indicated clearly in Fig. l. From an inspection of this ligure it will be seen that for each core one half of the laminations are placed on one side of the skeleton support and the other half on the other side, the parts being then secured together by bolts or screws.

For the purpose of holding thecurrent-coil 19 in position it is first secured to a plate 25 by means of bands of tape, as at 26, passing around the coil, through the opening therein, and through the opening in the plate where it fits over its core. The plate 25, carrying the current-coil, is then fastened to the skeleton support 24` by means of screws 27 27', passing through ears formed integral with the plate. It is of course evident, however, that the support for the current-coil may be otherwise secured, if desired.

The motive member of the meter above dcscribed is screwed or otherwise fastened to posts or projections on the frame or casing 1 of the meter. For this purpose holes are drilled in the skeleton support 24, as indicated at 28, 29, 30, and 31, through which screws are passed into projections formed on the casing 1 of the meter.

The disk 9 of the movable element of the meter rotates within the space between the opposing sets of polar projections on the motor element, and the motion induced by the motor element is communicated in the usual manner to a counter or registering device 32 of any ordinary construction. The usual dampingmagnets are employed for producing the required retarding torque for the meter, one of these magnets being shown in Fig. 1 at 33. In practice I generally find it necessary to employ more than one magnet.

In order to overcome the starting friction of the meter and to compensate for the effects of friction at light loads, I make use of a friction-compensating device 34. (Shown in side elevation in Fig. 1 and in plan view in Fig. 3.) As this device possesses no novel features, no special description thereof is necessary other than to state that the slight driving torque required is produced by means of a shifting field due to the distorting eect of a closed circuit conductor 35, located in an unsymmetrical position in the magnetic field between the pole-pieces 36 and 37 of the core of the exciting-coil 38, which in this instance is placed in series with the main potential-coil 10 of the meter, as clearly indicated in Fig. 2. In order not to obscure the other parts of the drawing, this device 34 is in this ligure shown out of the position chosen therefor, as in Fig. 1.

In order to prevent creeping of the meter, I

provide a wire 39, of magnetic material, projecting from the disk 9, so that as the disk rotates it moves toward and away from the damping-magnets. The damping-magnets attract the wire with a force which may be adjusted by bending it backward or forward or the like, so as to be just sufiicient to prevent the meter from creeping when there is no load on the meter.

In order to prevent interference between the magnetic fields due to the damping-magnets and vthe magnetic field of the motive element of the meter, I provide a magnetic screen 40, located between the magnets and the motive element, as indicated. The long narrow slot in the screen 40 affords a passage for the rotating disk 9, which projects through the slot and into the space between the opposing polepieces of the motive element, as shown.

When -the ineter is in operation, the main current fiowingin the main 11 passes through the current-coil 2O and produces a magnetic fiux, which passes through the vertical limb of the magnetic core, through the disk 9, and dividing completes its magnetic circuit through the air to the projecting ends of the horizontal portion 21 of the core. 'The polar projections 22 and 23 are therefore of-the same polarity.

A shunt-circuit across the mains of the system supplies current tothe potential-coil 1() of the meter. This current should lag as nearly as possible toninety degrees from the phase of the impressed electromotive force, this effect being secured by means of the magnetic core 11'. Most of Ythe iiux in thecore passes across Vthe air-gap 12'; but a certain small proportion is shunted through the polar projections 14 and15, the magnetic circuit being completed by the opposing polar projections 22 and 23 of the core of the current-coil. The fiux thus shunted through the polar projections 14 and 415is adjusted by means of the closed-circuited coil 16 in a well-understood manner, so that it lags exactly ninety degrees behind the phase of the electromotive force impressed upon-the potential-circuit. The flux passing through the disk 9'between the pole-pieces 14 and 22 is the resultant of two fiuxes, one in phase with the main current and the other displaced ninety degrees in phase from the impressed electromotiveforce. The iiux between the polar projections 15 and 23 is similarly compounded; but in this instance the potential-iiux is of opposite polarity, or, in other Words, displaced one hundred and eighty degrees in phase from the potential-fiux in the polar projection 14. lItwill therefore be evident that ashifting-field is produced which acts to exert torque upon the disk 9, this torque being proportionalto the true energy owing in the main circuit. Two

'iron screws, one only of which is shown at 41,

extend through the casing 1 toward the core 11'. These screws can be adjusted to assist in IOO IOS

preventing creeping by centering the mass of iron electrically with respect to the coils.

In the meter which I have above described it is evident that numerous changes may be made in the form and arrangement of the parts without departing in any essential particular from my invention, for which reason I desire that my claims should not be limited to the details shown nor otherwise than required by the state of the art.

What I claim as new, and desire to secure by Letters Patent of the United States, is-

1. In an electric meter, the combination of a core provided with a potential-coil, aslot or airgap in the magnetic circuit of said core, polar projections located on said core on either side oi' the said slot or air-gap, a current-coil having a separate core opposite to the polar projections of the first-named core, and a movable member disposed between said cores.

2. In an electric meter, a potential-coil, a rectangular core therefor having the continuity of one side of the rectangle interrupted by a slot or air-gap, polar projections on said core on either side of said slot or air-gap, a current-coil having a separate core opposite to said polar projections, and a movable member disposed between said cores.

3. In an induction-meter, the combination of a skeleton supporting member, two cores of magnetic material carried thereby, a portion of each of said cores being disposed on either side of said member, a current-coil inductively related to one of said cores, a potential-coil mounted on the other core, and a rotating member arranged within the inlinence of fluxes developed in both cores.

4. In an induction-meter, the combination of a rotating member, a core having anearlyclosed magnetic ci reuit, projecting pole-pieces on said core arranged in proximity to one side of said rotating member, a current-coil having polepieces.or polar projections opposite the first-mentioned core but separated therefrom by said movable member, and means on the first-mentioned core for adjust ing the phase of the iiux passing therefrom through said movable member.

5. In an induction-meter, a coil, a core therefor having a slot or air-gap in its magnetic circuit, and a pin driven between the walls of said slot so as to prevent alteration oi' the dimensions of the slot due to magnetic or other force that may be exerted upon the core.

6. In an induction-meter, the combination of a core provided with a potential-coil, a slot or air-gap in the magnetic circuit oi' said core, polar projections located on said core on either side of said slot or air-gap, a currentcoil having a separate core provided with polar projections opposite those on the core of the potential-coil, and a movable member for the meter movable between opposing faces of said polar projections,

7. In an electric meter, the combination of a core provided with a potentiahcoil, a cui rent-coil provided with a core, and a skeleton supporting device passing through the body of both cores and supporting the same.

8. In an induction-meter, the combination of a potential-coil, a core therefor provided with a slot or air-gap in its magnetic circuit, poiar projections on said core located on either side of said slot or air-gap, and means on said polar projections for displacing the phase of the flux therein relatively to the phase of the flux across said slot or air-gap.

9. In an induction-meter, the combination of a potential-coil, a core therefor provided Vwith a slot in its magnetic circuit, polar projections on said core located on either side of said slot, and means on said polar projections constituting the seat of induced currents.

v10. In an induction-meter,the combinationl of a current-coil, a magnetic core therefor having adjacent polar projections of the same polarity, a potential-coil, a core thereforprovided with polar projections oi' opposite polarity arranged opposite the polar` projections of the core of the cnrrent-eoil, and a movable member for the meter arranged within the influence of the iiux passing between the sets of polar projections.

In witness whereof I have hereunto set my hand this 28th day of February, 1903.

W'ILLIABI H. PRATT Witnesses:

DUGALD Meli. McKinnon, JOHN A. McManus. 

